Ground Stabilization Grid

ABSTRACT

A ground stabilization grid which includes a series of polygonal shaped cells having “x” sides. The cells are formed by polymer walls having a wall height of between about 1″ and about 6″. Each cell shares a common wall section with at least two adjacent cells; and a majority of cells within the grid includes at least two reinforcing ribs extending across the cell to engage opposing walls of the cell. The reinforcing ribs are characterized by (i) engaging the cell walls between about 25% and about 75% of the wall height, and (ii) extending between different opposing walls of the cell.

I. BACKGROUND

Various types of ground stabilizing systems are known in the art. Onesuch ground stabilizing system is the Dupont™ Plantex® Groundgrid® whichis formed of a plastic, expandable honeycomb grid structure. Theexpanded honeycomb grid is positioned on a ground surface and gravelplaced in the cells of the grid. However, these types of stabilizationsystems can be improved by making the grid itself more structurallystable. This is particularly the case if the grid is going to be used incombination with curable load bearing materials such as concrete.

II. SUMMARY OF SELECTED EMBODIMENTS OF INVENTION

One embodiment of the invention is a ground stabilization grid whichincludes a plurality of polygonal shaped cells having “x” sides. Thecells are formed by polymer walls having a wall height of between about1″ and about 5″. Each cell shares a common wall section with at leasttwo adjacent cells; and a majority of cells within the grid includes atleast two reinforcing ribs extending across the cell to engage opposingwalls of the cell. The reinforcing ribs are characterized by (i)engaging the cell walls between about 25% and about 75% of the wallheight, and (ii) extending between different opposing walls of the cell.

Another embodiment is a method of producing a ground stabilized pad. Themethod begins with positioning on a surface a stabilization grid. Thegrid includes (i) a plurality of closed cells formed by polymer wallshaving a wall height, each cell sharing a common wall section with atleast two adjacent cells; and (ii) substantially each cell including atleast one reinforcing rib extending across the cell to engage opposingwalls of the cell, the reinforcing ribs engaging the cell walls betweenabout 25% and about 75% of the wall height. The next step of the methodis filling the cells with a load bearing material.

III. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of one embodiment of the stabilizationgrid of the present invention.

FIG. 1B is a perspective view of the FIG. 1A stabilization grid rotated180°.

FIG. 2 is a perspective view of the opposite side of the FIG. 1Astabilization grid after concrete has been added to the grid cells.

FIG. 3 is a perspective view of an alternative embodiment of the groundstabilization grid.

FIG. 4 illustrates the FIG. 3 embodiment with concrete placed in thecells of the grid.

FIG. 5 illustrates the FIG. 1A stabilization grid employed in a turfsystem.

FIG. 6 illustrates the FIG. 3 stabilization grid employed in a turfsystem.

IV. DETAILED DESCRIPTION

FIG. 1A illustrates one embodiment of the stabilization grid 1 of thepresent invention. Generally, stabilization grid 1 will comprise aplurality of closed cells 2 formed by a series of walls 6. The cells 2will either be cells on the perimeter of grid 1 (perimeter cells 4) orcell inside the perimeter (interior cells 3). Each of the walls of theinterior cells 3 has a common wall 7 shared with an adjacent cell. Theperimeter cells 4 will typically have a common wall 7 with at least twoother cells. While the cells 2 can take on virtually any closed shape,in many embodiments, the cells are polygonal in shape. In other words, aclosed shape having at least three straight sides and angles between thesides. Such polygonal cells could have 3 (triangle), 4 (rectangle), 5(pentagon), 6 (hexagon), 7 (heptagon), or 8 (octagon) sides. The figuresillustrate hexagon cells. Each side or wall of the cells have a height“h”, which in preferred embodiments can range between 1″ and 6″ (or anysub-range in between), but in specialized embodiments, could be lessthan 1″ or greater than 6″. The width or “diameters” of the cells couldvary significantly from embodiment to embodiment. In the case of hexagonshaped cells such as in FIG. 1A, the maximum corner to corner distance10 across the cell (i.e., distance between furthest spaced corners) isbetween about 3″ and about 12″ (or any sub-range in between). Again, inspecialized embodiments, this corner to corner distance could be lessthan 3″ or more than 12″. The thickness of the cell walls could varydepending on material or design loads, but typically the cell wallthickness will range from 0.5 mm to 10 mm (or any sub-range in between).

In preferred embodiments, the cell walls will be formed of a polymermaterial. Nonlimiting examples may include polypropylenes, polyesters,or combinations thereof. Polymer materials can also include fiberreinforced polymer materials, e.g., resins which form polymers afterpolymerization or curing, e.g., fiberglass. In still other embodiments,it is conceivable the cell walls could be formed of ceramics or evenmetals.

FIG. 1A illustrates what will be considered the underside of the grid 1or side that will be facing the ground in many applications. Thus, FIG.1A shows all the cells 2 having open bottoms. Likewise, a majority ofthe cells in FIG. 1A have open tops. However, in the FIG. 1A embodiment,a minority of the cells will have closed tops 19, i.e., a top cellsurface formed of the same polymer material as the cell walls 6. FIG. 1Ashows the underside of closed tops 19 while the “upper” surfaces ofclosed tops 19 are seen in FIG. 2. In the illustrated embodiments, onlya single line of cells within the grid section is formed with closedtops 19. Grid 1 will typically have closed tops 19 when it is designedto attach a geofabric or other material over grid 1 as is explainedbelow. In embodiments where no material will overlay grid 1, it may bemore desirable to provide a grid 1 that has no closed top cells.

FIG. 1A also demonstrates how the cells 2 in the disclosed embodimentswill have some type of reinforcing rib 15 extending across the cell. Thecells 2 having open tops and bottoms will have straight-bar ribs 16. TheFIG. 1A embodiment shows each cell with two straight-bar ribs 16arranged in an intersecting cross pattern. However, other embodimentscould have a single straight-bar rib or more than two straight-bar ribs,e.g., six ribs for the hexagon cell seen in the figures. In preferredembodiments, the ribs 16 will be attached to the cell walls atapproximately the middle height (e.g., at about 50% of the height “h”seen in FIG. 1A). In other embodiments, the reinforcing ribs 16 willengage the walls at between about 25% and about 75% of the wall height.In other words, the ribs 16 will engage the cell walls at least 0.25 (h)above the bottom opening of the cell and at least 0.25(h) below the topopening of the cell. Still further embodiments will have the reinforcingribs 16 engaging the walls at between about 15% and about 85% of thewall height. In the illustrated embodiments, the cross-sectional area ofa rib 16 can vary between about 0.5 mm² to about 100 mm² (or anysubrange therebetween).

The cells having closed tops 19 are shown with a different ribconfiguration, fin-shaped ribs 20. Fin-shaped ribs 20 include wallconnecting section 21 which attaches along the length of the cell walls,and a joint connecting section 22 which attaches along the inner or“bottom” surface of closed tops 19 and join with the other ribs 20 atthe center of top 19. In the illustrated embodiment, a fin-shaped ribattaches at each wall of the cells with closed tops 19, but otherembodiments could have ribs attached to less than each wall in the cell.The fin-shaped ribs 20 provide extra rigidity to these cells because thecells with closed tops typically will not be filled with a load bearingmaterial as described further below. Cells with fin-shaped ribs 20 willhave at least twice as much total reinforcing material (bycross-sectional area of the ribs) as cells with the straight-bar ribs16.

In many embodiments, the grid 1 will be of a size to allow them to beeasily transported and handled by workers, e.g., 3′×3′, 4′×6′, etc.Thus, to cover a large area with the grid structure, it is advantageousto have individual grid sections connect to one another. The FIG. 1Agrid 1 includes such a means for attaching or interlocking additionalgrids to it. FIG. 1A shows how the outer wall of certain perimeter cellsmay include locking arms 30 which are formed by two arm extensions 31having a length approximate the cell height and oriented at about 45°with respect to the wall surface from which they extend. FIG. 1B showsthe opposite end of grid 1 with the perimeter cells having lockinggrooves 35 configured to mate with locking arms 30. It can be seen thatthe locking arms 30 and locking grooves 35 are positioned in a staggeredconfiguration or orientation, i.e., the locking arms 30 are offset onecell from the locking grooves 35 such that they may interlock. It can beseen that the grid perimeters, in essence, create alternating half-cellstructures 5 which form a continuous row of cells when joined with anadjacent grid section.

A somewhat modified version of the grid structure is seen in FIGS. 3 and4. FIG. 3 illustrates a grid structure 1 which is again composed ofjoined cells 2 formed by walls 6 shaped into interconnected hexagonclosed cells. Again, FIG. 3 is a view of what would normally beconsidered the “bottom” surface of the grid structure. However, in theFIG. 3 embodiment, there are six reinforcing ribs 15 in each cell.Moreover, the ribs 15 attach at the bottom of the cell wall rather thana mid-point of the cell wall as seen in FIG. 1A. FIG. 4 shows the FIG. 3grid structure filled with concrete, but not necessarily covering theribs 15.

Another aspect of the present invention is a method of producing aground stabilized pad using the stabilization structures describedherein. This method generally comprises positioning the stabilizationgrid on a surface and then filling the cells of the structure with aload bearing material. Using the FIG. 1A embodiment as an example,multiple grid sections 1 will be connected together using the lockingarms and locking grooves in order to create the desired surfaceconfigurations, e.g., a continuous elongated road surface, a rectangularparking surface, or the dimensions corresponding to a particular type ofsports field. In many embodiments, the surface onto which the structureis placed will be some type of prepared ground surface, for example anarea of compacted soil. This could be the case for a ground surface tobe used as a motor vehicle travel surface (e.g., a roadway or parkingarea) or a surface to be used as a sports field where the stabilizationpad is a base for an artificial turf system. The term “ground surface”is not limited to soil, but includes other surfaces previously existingon the ground, e.g., positioning the grid on a section of damagedpavement would be considered positioning on a “ground surface.” Ofcourse, the stabilization grid could be positioned on a ground surfacehaving no previous preparation (e.g., native soil). Likewise, thestabilization grid could be positioned on surfaces not associated withthe ground.

The load bearing material positioned within the grid cells can be anymaterial which at least initially has a flowable state allowing it tofill the cells and can then support substantial loads, eitherimmediately or after some period of curing. Sand and gravel are examplesof load bearing materials which can support loads immediately afterplacement. Concrete is an example of a load bearing material which mustcure prior to supporting a load. In many embodiments, the concrete usedwill be a conventional Portland cement based concrete having a curedstrength of at least 2500 psi. However, in other embodiments, the loadbearing material could be any material which is initially viscous, butlater becomes solid upon curing, such as ceramic based concretes, resinbased materials, or polymer based structural materials (also sometimesreferred to herein as “solid-curable compositions”).

Those skilled in the art will understand that the reinforcing ribs 15extending across the cells provide increase structural strength andstability to the overall stabilization system once the load bearingmaterial has been placed in the cells. Using Portland cement concrete asan example, once the concrete has cured, the reinforcing ribs not onlyenhance the load resistance of the concrete in the individual cells, butalso increase the resistance of the concrete to failing in response toflexure loads being applied across the grid system. In certainembodiments employing concrete, e.g., employing the system as a vehicletraffic surface, sufficient concrete will be poured over the gridstructure such that one or more inches of concrete cover the top of thecells.

As suggested above, one embodiment of the present invention is a methodof producing a ground stabilized pad by positioning a stabilization gridon a surface and filling the cells of the grid with a load bearingmaterial. In many embodiments, the stabilization grid is formed byinterconnecting a series of grids using a connecting means such as seenin FIGS. 1A and 1B. When the ground stabilized pad is being employed asa surface to support vehicle traffic, the load bearing material couldconceivably be sand or gravel, but more preferably will be concrete. Inmany instances when concrete is the load bearing material, sufficientconcrete will be placed over the grid sections such that at least 0.5″or 1″ of concrete covers the upper surface of the grid cell walls.

Other embodiments of the invention include an artificial turf system anda method of constructing the same. FIG. 5 illustrates one example of anartificial turf system 75 employing the stabilization grid seen in FIGS.1A and 1B. Turf system 75 generally includes the stabilization grid 1positioned on a compacted soil base, i.e., compacted subgrade 78. Awater impervious liner 79 is positioned between subgrade 78 and grid 1.In the FIG. 5 embodiment, the cells of grid 1 have been filled withPortland cement concrete (e.g., at least 2500 psi compressive strength),but alternative embodiments could employ other load bearing materials,including gravel. The cells of grid 1 will be filled to their top edgesas suggested in FIG. 2, leaving the closed tops 19 of the cellsuncovered by the concrete. Positioned on top of the concrete filled grid1 will be a drainage and shock attenuation blanket or layer 80. Whilethe drainage blanket 80 can be any one of a number of conventionaldrainage materials or fabrics, in the FIG. 5 embodiment, drainageblanket 80 is a GeoFlo® drainage and shock attenuation blanket availablefor Global Synthetics Environmental, LLC of St. Gabriel, La. Typically,the drainage blanket 80 is not attached to the grid, but iscomparatively free moving with respect to the grid. In certainsituations, the drainage blanket may be lightly and temporarily tackedor stapled to the closed tops 19 of the grid (e.g., in a windyconstruction environment. However, the drainage blanket may be moresecurely and permanently attached to the closed tops 19 along theperimeter of the grid field. In a similar manner, an artificial turflayer 82 is placed over the drainage blanket layer 80, but not rigidlyattached thereto except at the edges. Naturally, there can beapplications where the closed tops 19 of all grids (not just theperimeter grids) can be used to more securely attach some type of coverlayer or fabric (e.g., by stapling, tacking, or use of a glue or otheradhesive compound). In a preferred embodiment, the artificial turf layer82 may be a product such as GeoGreen® replicated grass also availablefrom Global Synthetics Environmental, LLC. A granular polymer infilllayer 83 is then applied to the artificial turf layer 82. In oneexample, the infill may be granularized rubber pellets ranging in sizefrom about 1/32 to ⅛ inch in diameter.

FIG. 5 further illustrates how the ends of drainage blanket and turflayers will be enclosed by the concrete border curb 87. The border curb87 will support a wooden nailer beam 88 via fasteners 89 extendingthrough nailer beam 88 into border curb 87. The edges of the drainageblanket and turf layer may then be fixed to nailer beam 88 by way of airnails, air staples, or screws, etc. Adjacent to the border curb 87 willbe the drainage channel 84 filed with aggregate such as No. 57 stone.The perforated drainage pipe 85 will be positioned at the bottom ofdrainage channel 84. Typically, the subgrade 78 will be formed to have agrade line 90 with at least a ½% slope falling toward the border curb87. Thus, rainfall on the turf system will be directed via drainageblanket 80 toward the drainage channel 84 and ultimately into drainagepipe 85.

FIG. 6 illustrates a slightly different embodiment of artificial turfsystem 75. The FIG. 6 embodiment is substantially the same as describedin reference to FIG. 5, but in FIG. 6, the grid system 1 seen in FIGS. 3and 4 is employed. The grid surface seen in FIG. 4 will be placedagainst the subgrade surface and the cells filled with concrete.Naturally, the grid structures seen in FIGS. 1A to 4 are only twoillustrative examples and artificial turf systems of the presentinvention could be constructed with many different grid configurations,particularly when the grid cells are being filled with concrete. As willbe apparent from the above description, the grid 1 is left in placewhile the concrete completely cures and the grid becomes an integralpart of the structural system (i.e., the grid is never removed afterplacement of the concrete).

The term “about” will typically means a numerical value which isapproximate and whose small variation would not significantly affect thepractice of the disclosed embodiments. Where a numerical limitation isused, unless indicated otherwise by the context, “about” means thenumerical value can vary by +/−5%, +/−10%, or in certain embodiments+/−15%, or even possibly as much as +/−20%.

1-19. (canceled)
 20. A ground stabilization grid comprising: (a) aplurality of polygonal shaped cells having “x” sides, the cells formedby polymer walls having a wall height of between about 1″ and about 5″;(b) each cell sharing a common wall section with at least two adjacentcells; (c) a majority of cells within the grid including at least tworeinforcing ribs extending across the cell to engage opposing walls ofthe cell, the reinforcing ribs (i) engaging the cell walls between about25% and about 75% of the wall height, and (ii) extending betweendifferent opposing walls of the cell.
 21. The ground stabilization gridof claim 20, wherein the at least two reinforcing ribs are positionedsubstantially perpendicular to one another.
 22. The ground stabilizationgrid of claim 20, wherein a majority of cells in the grid have open topsand bottoms.
 23. The ground stabilization grid of claim 22, wherein aminority of cells in the grid have an enclosed top.
 24. The groundstabilization grid of claim 23, wherein the cells with enclosed topshave at least twice the mass of reinforcing ribs as cells having opentops.
 25. The ground stabilization grid of claim 20, wherein a firstside of the grid includes a plurality of perimeter cells with outwardlyextending locking arms and a second side of the grid opposing the firstside includes a plurality of locking channels configured to receive thelocking arms.
 26. The ground stabilization grid of claim 25, wherein thecells with locking arms and the cells with locking channels arepositioned in a staggered configuration.
 27. The method of claim 50,wherein a corner to corner distance across the cells is between about 3″and about 12″.
 28. The method of claim 50, wherein the reinforcing ribsengage the cell walls between about 40% and about 60% of the wallheight.
 29. The ground stabilization grid of claim 20, wherein thereinforcing ribs each have a cross-sectional area of between about 3 mm²and about 30 mm². 30-49. (canceled)
 50. A method of producing a groundstabilized pad comprising the steps of: (a) positioning on a surfaceutilized for vehicle traffic a stabilization grid comprising: (i) aplurality of closed cells formed by polymer walls having a wall height,each cell sharing a common wall section with at least two adjacentcells; (ii) substantially each cell including at least one reinforcingrib extending across the cell to engage opposing walls of the cell, thereinforcing ribs engaging the cell walls between about 25% and about 75%of the wall height; (b) filling the cells with a Portland cement basedconcrete; and (c) allowing the concrete to completely cure while leavingthe grid in place.
 51. The method of claim 50, wherein the concrete hasa strength of at least 2500 psi.
 52. The method of claim 50, wherein (i)a first side of the grid includes a plurality of perimeter cells withoutwardly extending locking arms and a second side of the grid opposingthe first side includes a plurality of locking channels configured toreceive the locking arms; and (ii) a plurality of grids are inter-lockedtogether prior to placing concrete in the cells.
 53. The method of claim50, wherein sufficient concrete is placed over the grid to provide atleast 1″ of concrete cover over the top of the cells.
 54. The method ofclaim 50, wherein the reinforcing ribs each have a cross-sectional areaof between about 3 mm² and about 30 mm².